Dead bulkhead



Jan- 21, 1954 c. BABER ETAL 3,118,211

DEAD BULKHEAD Filed Nov. 13, 1962 BY ROBERTLKAHN ATM United States Patent C) 3,118,211 DEAD BULKHEAD Claude haber, Kettering, Donald E. Jackson, Vandalia, and Warner B. Smith, ayton, Ollio, assignors to The Flexicore Co., Inc., Brayton, Ohio, a corporation of New York Filed Nov. 13, 1962, Ser. No. 236,854 3 Claims. (Cl. 25-118) This invention relates to a slab casting means and more particularly to a bulkhead for use at the end of a form for casting concrete slabs, Concrete slabs, particularly of the prestressed type, have been manufactured for many years in various lengths up to as much as 50 feet. As an example, United States Patent No. 2,299,111 discloses a form for casting slabs. These slabs have passages longitudinally thereof for improving the stress characteristics as well as conserving concrete.

In order to prestress slabs of this character, steel strands are disposed longitudinally of the slab and maintained under tension until the slab has been cast and cured. The location of such strands in a slab will depend upon the desired characteristics or the slab. Usually strands are disposed in the lower corner portions of the bottom of a slab as well as in the lower center part of the slab between longitudinal passages. Additional prestressing Strands may be disposed in the upper corner portions of the slab. For example, United States Patent No. 2,956,375, issued October 18, 1960, to Henry, shows a prestressed slab having a full complement of prestressing strands along the bottom portions of the slab as Well as the top portions thereof. Prestressed slabsand for that matter, unstressed slabs-are cast in casting forms having a generally U- shaped cross section. Each such casting form must have at least one so called dead bulkhead at the very end thereof. An additional dead bulkhead may be provided at the other end of the casting form and if more than one slab is cast at one time in a casting form, intermediate so called live bulkheads are disposed. Such intermediate live bulkheads in their simplest form function merely as partitions to conne the concrete mix. The slab casting accessories such as prestressing strands, cores for `defining longitudinal passages in the slab, extend through such live bulkheads. insofar as the cores are concerned, these being used to denne longitudinal passages, a dead bulkhead is similar to a live bulkhead in that windows or openings through the bulkhead must be provided for the cores to extend through the bulkhead.

The provision of windows or openings in a dead bulkhead for cores creates a bulkhead design problem due to the weakening of the dead bulkhead. It is the prestressing strand terminations which create serious stress problems in a dead bulkhead. A dead bulkhead must not only function to provide an end wall for the slab casting region but must be able to provide the enormous reactive forces for maintaining all tensioned prestressing strands during initial setting up of the form as well as during casting and curing of a slab.

Prestressing strands pass through openings in a dead bulkhead wall and are initially tensioned by jacks. Thereafter, the tensioning load is transferred to strand chucks or other gripping means. The jacks and strand chucks must be braced against the dead bulkhead wall. insofar as strand chucks are concerned, the reactive force for maintaining a strand in tension must be exerted by the bulkhead wall in a region immediately surrounding the opening through which a strand passes. insofar as strand tensioning jacks are concerned, the region of the bulkhead for reacting to the tension is generally at diiferent and scattered locations. The force required to maintain a single strand at desired full tension in present day slabs llll Patented Jan. 2l, 1954 ICC can be in excess of l0 tons. With one slab having from three to as many as six separate prestressing strands, the total force acting upon a dead bulkhead may range from 30 tons to over 50 tons.

When setting a casting form in preparation for casting, the prestressing strands are not simultaneously tensioned. As a rule, the tension is applied to individual strands in succession and after the desired tension has been obtained, it is maintained by a chuck or similar gripping means. A dead bulkhead does not have its enormous total load applied evenly or symmetrically with respect to the center of such a bulkhead.

It is evident, therefore, that the design of a dead bull'- head involves unusual structural problems. Apart from the structural problems presented by the tremendous forces which a dead bulkhead must withstand are practical considerations relating to the every-day use of such bulkheads in casting slabs. As previously pointed out, the passage-forming core, as well as prestressing strands, pass through openings in the dead bulkhead wall.

From the nature of industrial operations in this iield, it is impractical to have tine clearances between the bulkhead wall and the prestressing strands. This is particularly true if different sizes of wire are used with the same bulkhead. The clearance regions are often caulked after the form is set up for casting. ln any event, concrete mix will frequently ooze or work its way around the strand through the bulkhead opening. This escaping concrete mix will reach the strand chucks in spite of spacers between the chucks and dead bulkhead wall which are provided for ease in burning the strand to remove the strand chuck. Strand chucks generally, have precision ground parts and have hardened steel jaws or gripping surfaces. The presence oi abrasive concrete is injurious to the life of such strand chucks. Each time a casting form is set up, it is necessary that any deposits of concrete from previous operations be thoroughly clemed away from and removed from the dead bulkhead and this can i'lnd its way into the strand chucks.

Once a slab has been cast and cured, it is necessary to remove the casting. This involves the endwise removal of the core or cores from the casting, as well as the dead bulkhead. Before the bulkhead can be removed, the surplus strand and chucks must be removed, usually by cutting or burning the strand metal between chuck and bulkhead.

Another important consideration in the design of a dead bulkhead involves the maintenance of strand tension of one or more strands as additional untensioned strands are being tensioned themselves. The dead bulkhead must have suicient rigidity so that the value of nal tension applied to any one or more prestressing strands will not be disturbed by the application of tension to remaining prestressing strands. Any substantial yielding or distortion of the dead bulkhead will change the strand tension. Thus as an example, if there are three prestressing strands, and if No. l strand has been prestressed to the desired value, it is important that this value be maintained within close limits and not be exceeded, then when strand No. 2 is being tensioned, the tension in strand No. 1 should not be disturbed in any substantial degree during the build-up of tension in No. 2 strand. The same considerations apply to No. 3, in which case the tensions in both No. l and No. 2 should be maintained at desired values. Furthermore, it is important that this relationship hold true irrespective of the order in which these strands are tensioned.

ln accordance with the present invention, l have provided a new bulkhead for use at the end of a slab casting form, said bulkhead having substantial advantages over present day bulkheads. The new bulkhead embodying the present invention provides two spaced wall portions to atraen separate the functions of terminating the casting region and supporting the strand grLping means for tensioning the prestressing strands. Thev new bulkhead is light enough so that it can be easily handled and provides readily accessible regions where short lengths of prestressing strands are exposed for cutting by suitable means such as a torch, cutters or saws. In addition, the new bulkhead construction provides a region where waste concrete mix may fall, this region being spaced from where workmen would stand in connection with operating on the end of the casting form and spaced from the strand gripping means. The new bulkhead makes it possible to keep the strand chucks or other strand gripping means clean and free from concrete mix and provides a wall between the chuck and the wall terminating the casting region. Because of this second wall, no spacer between a strand chuck and second wall is necessary, unless take-up shims or spacers are used at the pulling end of the casting form to take up excess strand length.

For an understanding of the invention, reference will now be made to the drawing showing a perspective view of the new bulkhead embodying the present invention.

The new bulkhead comprises front wall 16 and rear wall 11 disposed in spaced generally parallel relation. The entire bulkhead is made of steel, and has the various parts, to be described, welded together to form a unitary, rigid structure. Front wall is adapted to be disposed against the end or a slab casting form such as, for example, the Casting form disclosed in the patent referred to previously. Front wall 10 has support lugs 14 and 15 at the ends and is suiiiciently long (across the end of the casting form) so that support lugs 14 and 15 extend beyond the outer sides of the casting form. Lugs 14 and 15 have recessed portions 16 and 17 which can slide over Supporting pins welded to the sides of a casting form and extending beyond the ends thereof. Such pins are illustratedin EGURE ll of the patent referred to and are identified by numeral 57 therein. Front wall 1d engages 'the edges ofthe sides and bottom of the casting form.

Front wall 1li is provided with windows or openings 19 and Ztl therethrough for accommodating cores which will be disposed within the casting form for the purpose of detining longitudinal passages in the slabs. As illustrated here, openings 19 and 2t) are circular and will accommodate inflatable cores. However, these core openings may have other shapes for accommodating different kinds and shapes of cores.

ln addition to the openings for cores, front wall 1i! is provided with openings 22 at selected positions for accommodating prestressing strands. As many openings for prestressing strands may be provided as are deemed necessary and in the event that some of these openings are not required for certain slabs, plugs of rubber or metal may be used to block the undesired openings. Openings 22 are large enough to accommodate the heaviest gauge strand.

Front wall 10 has top plate 25 which extends from front wall 141 rearwardly toward rear wall 11 for only part of the distance. Top plate 25 is welded or otherwise rigidly attached to the top edge of front wall 10 and has end plates Z6 and 27 welded thereto to form a partial enclosure.

Rear wall 11 has welded thereto bottom panel 33 Whose forward edge 34 stops short of front wall 10. The bulkhead is provided with side plates 35 and 36 which extend between front wall Il@ and rear wall 11 and are welded thereto, as well as to bottom panel 33. Side plates 35 yand 35 are flat steel plates which are in non-parallel vertifcal planes, in the normal position of the bulkhead when used with a casting form. The distance between the side plates is less along rear wall `11 as compared to front wall 10. The disposition of side plates 35 and 36 wl be explained later. The tops of side plates y35 yand 36 are notched deeply at 4@ and 41 respectively, each notch having the general shape of a V. The bottom of the notch is `at Vor somewhat b elotv the level of prestressing strand openings 22 and the notches are wide enough to permit application of a torch, saw or cutting tool to a prestressing strand between the front and rear walls and immediately adjacent the side plates.

In addition to side plates 35 and 36, intermediate brace plates 43 and 44 are provided, these plates extending between the front and rear plates and being welded thereto. Intermediate brace plates 43 and 44 as seen in elevation from the rear of the bulkhead are bent so that the two wall portions together form an inverted Y, with the inverted bottom of the Y consisting of two parallel portions 45 and d6 slightly spaced from each other and diverging portions 47 and 43. The inverted Y straight portions 45 and 46 are welded to top plate 25 and upper part of front wall 1t?. Diverging brace plate portions #i7 and 4S are welded to the lower part oi front wall 1d and to bottom panel 33. The shapes of intermediate brace plates 43 and de and the positioning thereof are selected so that they will clear adjacent core openings 19 and Eil adjacent prestressing strands.

intermediate brace plates 43 and i4 resemble side plates 35 and 35 in that they have V notches 5d and 51 extending from the top edges thereof. V notches do and 51 are aligned with V notches 4G and 41 ot' the side plates. Notches 5S and 51 thus give ready access to prestressing strands. Side plates 35 and 36 stop a bit short of top plate 25, though could extend thereto, whereas intermediate brace plates 43 and 44 extend to and are welded to the inside face of top plate 25. At rear wall 11, the side and brace plates stop at about the horizontal diameters of core openings 19 and 26. The top edge of rear wall 11 curves inwardly at 52 and 53 to provide smooth semicircular rests which register with the bottom halves of core openings 19 and Ztl in front wall 1t). This makes it easier to handle cores. Rear wall 11 has strand openings 22a which are alined with corresponding strand openings 22 in front plate 10.

Additional openings 55 near the bottom of rear wall 11 may be provided to accommodate pins or" hydraulic jacks which can be positioned outside of the bulkhead against rear wall 11 for the purpose of tensioning the prestressing strands. These openings are located adjacent the edges of the side or intermediate plates 35, 36, 43 and 44.

Gusset plate 55 is welded to the inside surfaces of side plate 40, brace plate 43 and rear wall 11. Gasset plate 56 is inclined so that at rear wall 11, it is below the outermost strand clearance opening 22a and below curved edge 52, with the forward part of the gusset plate being welded to edge 34. Gusset plate 57 is similarly positioned between brace plate 44, side plate 36, rear wall 11 and edge 34. The space between edge 34 and the rear face of front wall 11 at the bottom of the bulkhead is open. The location of the gusset plates provides reinforcement of rear wall 11 at the regions where strand chucks bear against the end portions of the rear wall. Similarly, the gusset plates straddle the strand opening in the middle part of wall 11 and reinforce it. ln order to reduce weight, it is possible to have cut-outs in bottom panel 33.

The entire bulkhead provides a strong construction which can withstand considerable abuse and will effectively function as a dead bulkhead for the end of a casting form. Strand chucks 6l? for holding prestressing strands 61 in tension will be braced against the rear face of rear wall 11. Whatever concrete leaks through front wall lil will fall into the open space between edge 34 and front wall 1t). The distance between front wall 1% and rear wall 11 will be suicient so that exposed tensioned strands between walls 19 and 11 are readily accessible for severing, sawing or cutting after a casting has been cured. In practice, the separation between walls 10 and11 may be of the order of about 5" but can be made to suit individual requirements.

Any debris from prestressing strands, after severing, Will fall on sloping gusset plates 56 and 5'7 and drop toward the open space at the bottom of the bulkhead adjacent front wall 10.

Referring now to side plates 35 and 36, these are proportioned so that the front edges of these side plates will engage front wall along regions which register with edges 63 of sides 64 of the casting form when the bulkhead is in position. The rear edges of side plates and 36 will engage rear wall 11 laterally of strand clearance openings 22a on the far sides of these openings. The side plates are quite close to these strand openings 22a. Because of this side plate arrangement, the force of the strand chucks at the end strands will be assumed to a substantial degree by end plates 35 and 36 and communicated through front wall 10 to edges 63 of the casting form.

What is claimed is:

l. A dead bulkhead for use with forms for casting long concrete slabs, said forms in the casting condition having a general channel-shaped section, said slabs having longitudinal passages therethrough formed by cores and said slabs having prestressing strands extending 1ongitudinally thereof along the lower portion of a slab, said bulkhead comprising an integral rigid steel structure having, in normal position of use, spaced generally parallel front and rear walls lying in vertical planes, the front wall having a flat front outer face to abut the end of a casting form for closing the casting region, said front wall having clearance openings for slab passageforming cores and for prestressing strands, said rear Wall having alined openings for prestressing strands and having the top edge thereof shaped so that a core disposed in the corresponding opening through the front Wall can rest upon the top edge of the rear wall, side plates extending between the front and rear walls and rigidly joined thereto, the side plates lying in vertical planes but being non-parallel, the side plates being joined to the rear wall close to a strand clearance opening, each side plate meeting the front wall at a region which is alined with the edges of the sides of the casting slab when said bulkhead is in position, said side plates having deep V notches extending downwardly from the top edges thereof with the bottom of each notch being about level with the adjacent prestressing strand when the bulkhead and casting form is in condition for casting, each such notch being large enough to permit ready access from the top of the bulkhead and the top of each side plate to exposed adjacent prestressing strands for the purpose of severing the portions of strands between the front and rear walls, two intermediate brace plates disposed between said front and rear walls and between said two side walls, said brace plates when viewed through the rear wall and looking toward the front wall, being shaped to appear as an inverted Y, the leg of the Y (the bottom portion of the Y in the normal Y position) lying between adjacent core openings and the diverging legs of the Y extending on opposite sides of centrally disposed prestressing strand openings, said brace plates having deep notches inwardly of the top edges thereof generally similar and alined with the corresponding notches in the side plates, a gusset plate extending between the inside face of the rear wall and going toward but stopping short of the bottom edge of said front wall, said gusset plate being rigidly joined to the rear wall and to an adjacent intermediate brace plate and sloping downwardly from a line along the rear wall which is just below the top edge of the rear wall where the core can rest and is also below the level of the clearance openings for the prestressing strands, a second gusset plate corresponding to the first and located correspondingly between the remaining side wall and remaining brace plate, a plate welded to the top edge of said front wall and extending horizontally across the bulkhead and toward the rear Wall for a part of the distance only between the front and rear walls, said last named plate being welded to the top edges of the intermediate brace plate portions adjacent the front wall, said structure being made of heavy steel and utilizing said steel efficiently so that when said bulkhead is in position, there will not be any significant buckling or yielding of the bulkhead as prestressing strands are tightened, said bulkhead maintaining the prescribed strand tensions after they have been attained during casting and curing of the slab, said bulkhead providing ready access for severing prestressing strands after the casting has been cured and also providing sulcient space and a protective wall for strand chucks resting against the outside face of the rear wall so that such chucks can be maintained clean and free of concrete, the open space at the bottom of said bulkhead permitting any concrete which leaks through the openings in the front Wall to drop free of the bulkhead.

2. The construction according to claim 1 wherein said front wall has mounting extensions laterally at the ends thereof, said extensions including means for hanging said bulkhead against the end of said casting form.

3. The construction according to claim 2 wherein said rear wall has jack locating means along the bottom portion thereof.

References Cited in the le of this patent UNITED STATES PATENTS 977,345 Tidnam et al. Nov. 29, 1910 1,000,089 Haas Aug. 8, 1911 2,966,717 Fuller et al. Jan. 3, 1961 

1. A DEAD BULKHEAD FOR USE WITH FORMS FOR CASTING LONG CONCRETE SLABS, SAID FORMS IN THE CASTING CONDITION HAVING A GENERAL CHANNEL-SHAPED SECTION, SAID SLABS HAVING LONGITUDINAL PASSAGES THERETHROUGH FORMED BY CORES AND SAID SLABS HAVING PRESTRESSING STRANDS EXTENDING LONGITUDINALLY THEREOF ALONG THE LOWER PORTION OF A SLAB, SAID BULKHEAD COMPRISING AN INTEGRAL RIGID STEEL STRUCTURE HAVING, IN NORMAL POSITION OF USE, SPACED GENERALLY PARALLEL FRONT AND REAR WALLS LYING IN VERTICAL PLANES, THE FRONT WALL HAVING A FLAT FRONT OUTER FACE TO ABUT THE END OF A CASTING FORM FOR CLOSING THE CASTING REGION, SAID FRONT WALL HAVING CLEARANCE OPENINGS FOR SLAB PASSAGEFORMING CORES AND FOR PRESTRESSING STRANDS, SAID REAR WALL HAVING ALINED OPENINGS FOR PRESTRESSING STRANDS AND HAVING THE TOP EDGE THEREOF SHAPED SO THAT A CORE DISPOSED IN THE CORRESPONDING OPENING THROUGH THE FRONT WALL CAN REST UPON THE TOP EDGE OF THE REAR WALL, SIDE PLATES EXTENDING BETWEEN THE FRONT AND REAR WALLS AND RIGIDLY JOINED THERETO, THE SIDE PLATES LYING IN VERTICAL PLANES BUT BEING NON-PARALLEL, THE SIDE PLATES BEING JOINED TO THE REAR WALL CLOSE TO A STRAND CLEARANCE OPENING, EACH SIDE PLATE MEETING THE FRONT WALL AT A REGION WHICH IS ALINED WITH THE EDGES OF THE SIDES OF THE CASTING SLAB WHEN SAID BULKHEAD IS IN POSITION, SAID SIDE PLATES HAVING DEEP V NOTCHES EXTENDING DOWNWARDLY FROM THE TOP EDGES THEREOF WITH THE BOTTOM OF EACH NOTCH BEING ABOUT LEVEL WITH THE ADJACENT PRESTRESSING STRAND WHEN THE BULKHEAD AND CASTING FORM IS IN CONDITION FOR CASTING, EACH SUCH NOTCH BEING LARGE ENOUGH TO PERMIT READY ACCESS FROM THE TOP OF THE BULKHEAD AND THE TOP OF EACH SIDE PLATE TO EXPOSED ADJACENT PRESTRESSING STRANDS FOR THE PURPOSE OF SEVERING THE PORTIONS OF STRANDS BETWEEN THE FRONT AND REAR WALLS, TWO INTERMEDIATE BRACE PLATES DISPOSED BETWEEN SAID FRONT AND REAR WALLS AND BETWEEN SAID TWO SIDE WALLS, SAID BRACE PLATES WHEN VIEWED THROUGH THE REAR WALL AND LOOKING TOWARD THE FRONT WALL, BEING SHAPED TO APPEAR AS AN INVERTED Y, THE LEG OF THE Y (THE BOTTOM PORTION OF THE Y IN THE NORMAL Y POSITION) LYING BETWEEN ADJACENT CORE OPENINGS AND THE DIVERGING LEGS OF THE Y EXTENDING ON OPPOSITE SIDES OF CENTRALLY DISPOSED PRESTRESSING STRAND OPENINGS, SAID BRACE PLATES HAVING DEEP NOTCHES INWARDLY OF THE TOP EDGES THEREOF GENERALLY SIMILAR AND ALINED WITH THE CORRESPONDING NOTCHES IN THE SIDE PLATES, A GUSSET PLATE EXTENDING BETWEEN THE INSIDE FACE OF THE REAR WALL AND GOING TOWARD BUT STOPPING SHORT OF THE BOTTOM EDGE OF SAID FRONT WALL, SAID GUSSET PLATE BEING RIGIDLY JOINED TO THE REAR WALL AND TO AN ADJACENT INTERMEDIATE BRACE PLATE AND SLOPING DOWNWARDLY FROM A LINE ALONG THE REAR WALL WHICH IS JUST BELOW THE TOP EDGE OF THE REAR WALL WHERE THE CORE CAN REST AND IS ALSO BELOW THE LEVEL OF THE CLEARANCE OPENINGS FOR THE PRESTRESSING STRANDS, A SECOND GUSSET PLATE CORRESPONDING TO THE FIRST AND LOCATED CORRESPONDINGLY BETWEEN THE REMAINING SIDE WALL AND REMAINING BRACE PLATE, A PLATE WELDED TO THE TOP EDGE OF SAID FRONT WALL AND EXTENDING HORIZONTALLY ACROSS THE BULKHEAD AND TOWARD THE REAR WALL FOR A PART OF THE DISTANCE ONLY BETWEEN THE FRONT AND REAR WALLS, SAID LAST NAMED PLATE BEING WELDED TO THE TOP EDGES OF THE INTERMEDIATE BRACE PLATE PORTIONS ADJACENT THE FRONT WALL, SAID STRUCTURE BEING MADE OF HEAVY STEEL AND UTILIZING SAID STEEL EFFICIENTLY SO THAT WHEN SAID BULKHEAD IS IN POSITION, THERE WILL NOT BE ANY SIGNIFICANT BUCKLING OR YIELDING OF THE BULKHEAD AS PRESTRESSING STRANDS ARE TIGHTENED, SAID BULKHEAD MAINTAINING THE PRESCRIBED STRAND TENSIONS AFTER THEY HAVE BEEN ATTAINED DURING CASTING AND CURING OF THE SLAB, SAID BULKHEAD PROVIDING READY ACCESS FOR SEVERING PRESTRESSING STRANDS AFTER THE CASTING HAS BEEN CURED AND ALSO PROVIDING SUFFICIENT SPACE AND A PROTECTIVE WALL FOR STRAND CHUCKS RESTING AGAINST THE OUTSIDE FACE OF THE REAR WALL SO THAT SUCH CHUCKS CAN BE MAINTAINED CLEAN AND FREE OF CONCRETE, THE OPEN SPACE AT THE BOTTOM OF SAID BULKHEAD PERMITTING ANY CONCRETE WHICH LEAKS THROUGH THE OPENINGS IN THE FRONT WALL TO DROP FREE OF THE BULKHEAD. 